The present invention relates to a method for automatically focusing a camera, in particular a video monitoring camera.
“Smart cameras” are understood to mean optical systems that not only record images but can also process them and/or interpret them themselves. In addition to having an image recording function, a smart camera, as an intelligent and autonomous optical system, can, for example, extract and process application-specific information from recorded images and make decisions based thereon.
Smart cameras, which are frequently used in the context of monitoring tasks, generally consist of a camera housing having a video processing unit (Video Content Analysis) and a removable lens. Depending on the application, different lenses (wide-angle lens, telephoto lens or zoom lens) can be used. After a new lens is mounted, it must generally be focused manually. Smart cameras are to this end typically connected to a computer (for example a notebook) via a network connection, for example via the Ethernet or WLAN. Subsequently, the camera image can be viewed on the notebook, while the lens is set to the best focus.
A further application is the use in what are known as autodome cameras, which have motors for panning, tilting and zooming (PanTiltZoom). In these cameras, the focus needs to be reset after each case of being directed to a new position.
A focusing device used in such smart cameras or a taking lens with variable focal length is disclosed, for example, in DE 23 61 286 A1. Automatic methods for motorized focusing of a lens (also referred to as autofocus methods) are known, for example, from DE 692 07 043 T2.
DE 10 2010 039 431 A1 discloses an apparatus for supporting manual focusing of a camera, in particular a smart camera.
For automatically focusing a camera, it is also possible to adjust the focus until the contrast measured within the image is as good as it can be. However, this sometimes takes a long time, since, as a result of iterative attempts, initially a setting in the wrong direction may be effected.
Therefore, there is a need for a method for automatically focusing corresponding cameras, in particular smart cameras in the monitoring field, which ensures quick focusing.